(1) Field of the Invention
The present invention relates to a charged particle beam exposure system such as an electron beam exposure system using a line of individual blanking apertures.
(2) Description of the Related Art
Recently, direct exposure lithography for large scale integrated circuits (LSI's), i.e., electron beam exposure lithography without masks has been broadly developed. Such electron exposure lithography often uses a variable shaped beam such as a variable rectangular beam to enhance the throughput of an electron beam exposure system.
However, as the fine configuration of LSI's develops, variable shaped beam exposure systems have the following disadvantages, particularly in the production of LSIs having line widths in the order of 0.2 to 0.3 .mu.m:
(1) There is an upper limit to the current densities that can be achieved by using variable shaped beams.
(2) In order to project LSI pattern requiring a large number of shots, the number of driver (DAC/AMP) adjustments necessary for main deflectios, a sub deflections and a beam size deflection must be increased, thus increasing wasted time. Therefore, variable shaped beam exposure systems are not adapted to the mass production of fine patterns consisting of 0.2 to 0.3 .mu.m lines.
(3) A shaped beam having a width of 0.2 to 0.3 .mu.m is too small, to be practical since such a shaped beam is the same as a point beam which has no merit.
(4) Since variable shaped beams are generally formed by superimposing two separate masks, the doses of small beam such as those having a width 0.2 to 0.3 .mu.m are all relatively unstable.